Our objective is to isolate and characterize abnormal membrane components that are specific to or associated with human leukemia cells or malignant lymphoma cells, and to isolate as well normal membrane components, especially normal alloantigenic components of human lymphocytes that are linked to particular immunologic functions. Human lymphoid cell lines are being used for this purpose since they are a very good source of these immunobiologically important cell products. They retain a variety of biological functions and they represent a uniform cell population whose supply can be relatively unlimited in amount. We are also investigating similar cell surface antigens from cultures of other malignant cells, i.e., sarcoma and carcinoma cells, which are available in this laboratory. Membrane glycoproteins from a number of T-cell type and B-cell type cell lines will be isolated by lectin or antibody affinity chromatography. We also plan to isolate membrane glycoproteins from a number of man-mouse cell hybrid clones that carry particular human chromosomes and prepare mouse antisera against them. By use of such antisera, we will identify membrane components that are characteristic of a reduced number of the human components of the original human cell line. We will investigate expression of HLA antigens and human Ia antigens in primary malignant tumors. The human homologues of mouse thymus-leukemia antigens (TLa antigens) in human thymus and in human leukemic T-cell type cell lines will be identified. Human Ia(-like) antigens from human B-cell type cell lines and from non-lymphoid organs will be isolated and analyzed for their genetic and antigenic properties and the chemical nature of component peptides. The very sensitive quantitative radioimmunoassay method involving the use of radioiodinated reference antigen, which has been extensively employed by us in earlier studies, facilitates identification and isolation of the membrane components.